In general, a rotating electrical machine such as a motor, a generator and the like to be mounted on a vehicular transaxle for an automotive vehicle is constructed to include a rotatable rotor, and a stator having a stator core provided around the outer circumferential portion of the rotor and a stator coil wound around the stator core.
The motor can obtain rotational force when the stator coil is energized, while the generator can be drawn electric current flowing in the stator coil by the rotation of the rotor.
When the rotor is rotated to have the electric current flow in the stator coil, there is caused heat in the stator core and the stator coil. The heat of the stator core and the stator coil affects magnetic flux penetrating through the inner portions of the motor and the generator, thereby decreasing operating efficiency (rotation efficiency, generation efficiency). It is therefore required to cool the rotating electrical machine in order to maintain the operating efficiency.
The rotating electrical machine as mentioned above is mounted on a vehicle in the form of being covered by a case. Therefore, there are many cases in which the rotating electrical machine is cooled by oil passing through an oil passage formed in the case, viz., the rotating electrical machine is applied with liquid cooling.
A typical example known as a conventional cooling structure of this kind of a power transmission apparatus is shown in FIG. 5 (see for example Patent Document 1).
In FIG. 5, there is provided a rotating electrical machine 2 provided in a case 1 of a vehicular transaxle and has a rotor 3, and a stator 4 provided around the rotor 3 to surround the rotor 3.
The rotor 3 is mounted on a shaft 5 extending along the center line of the rotor 3. The shaft 5 is rotatably supported on the case 1 through a bearing 1a. 
The stator 4 comprises a stator core 6, and a stator coil 7 wound around the stator core 6, so that the stator coil 7 energized can generate a magnetic field which in turn forms a magnetic flux between the rotor 3 and the stator 4 to make the rotar 3 obtain the rotational force.
Inside the case 1, provided is an oil pipe 8 which is positioned above the rotating electrical machine 2 and has an inner passage allowing the oil to pass therethrough. The oil pipe 8 is adapted to allow the oil to pass therethrough when the oil stored in an oil pan 9 provided at the lower portion of the case 1 is drawn up by an oil pump 10.
The oil pipe 8 is formed with discharge nozzles 8a in face-to-face relationship with the coil ends 7a of the stator coil 7 outwardly projecting from both axial ends of the stator core 6 so that the oil flowing in the oil pipe 8 can be discharged to the coil ends 7a from the discharge nozzles 8a. 
The oil discharged to the coil ends 7a is designed to fall along the peripheral portions of the coil ends 7a that is heated to a highest temperature in the stator coil 7 to the lower portions of the coil ends 7a. While the oil falling from the coil ends 7a, the heat of the coil ends 7a is transmitted to the oil, thereby cooling the stator 4.